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Re: Need a function to multiply the elements of an array [message #4056 is a reply to message #4052]

Thu, 27 April 1995 00:00

adorf
Messages: 4
Registered: August 1994

Junior Member

In article <3nm2uk$qqq@pinot.umd.edu>, barsam@Glue.umd.edu (Barsam
Marasli) wrote:

> Hi,
>
> I am looking for a routine to multiply the elements of an array.
> Is there a faster way of doing it than the following?
>
>
> function prod, x
> n = n_elements(x)-1
> z = 1.d0
> for i = 0, n do z = z * x(i)
> return, z
> end
>
>
>
> BM

You can try

z = exp(total(alog(x)))

Whether it is faster than your function, I do not know. On my Sparcstation
2 it took 2 seconds to multiply 1 million numbers.

Regards
Hans-Martin

PS: I think that apart from the function 'total' (which might more
appropriately be called 'sum') there should be a native IDL function
'prod' doing what you do by hand.

--
Hans-Martin Adorf
ST-ECF/ESO
Karl-Schwarzschild-Str. 2
D-85748 Garching b. Muenchen
Germany
Tel: +49-89-32006-261
Fax: +49-89-32006-480
Internet: adorf@eso.org

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[Message index]

		Re: Need a function to multiply the elements of an array By: barsam on Thu, 27 April 1995 00:00
		Re: Need a function to multiply the elements of an array By: adorf on Thu, 27 April 1995 00:00
		Re: Need a function to multiply the elements of an array By: dan on Wed, 26 April 1995 00:00

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